Polarized 3D system

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Circularly polarized 3D glasses in front of an LCD (Liquid Crystal Display) tablet with a quarter-wave retarder on top of it; the l/4 plate at 45deg produces a definite handedness, which is transmitted by the left filter but blocked by the right filter. Circular polarization demonstrated with stereo glasses and iPad.JPG
Circularly polarized 3D glasses in front of an LCD (Liquid Crystal Display) tablet with a quarter-wave retarder on top of it; the λ/4 plate at 45° produces a definite handedness, which is transmitted by the left filter but blocked by the right filter.

A polarized 3D system uses polarization glasses to create the illusion of three-dimensional images by restricting the light that reaches each eye (an example of stereoscopy).

Contents

To present stereoscopic images and films, two images are projected superimposed onto the same screen or display through different polarizing filters. The viewer wears low-cost eyeglasses which contain a pair of different polarizing filters. As each filter passes only that light which is similarly polarized and blocks the light polarized in the opposite direction, each eye sees a different image. This is used to produce a three-dimensional effect by projecting the same scene into both eyes, but depicted from slightly different perspectives. Multiple people can view the stereoscopic images at the same time.

Types of polarised glasses

Linearly polarised glasses

To present a stereoscopic motion picture, two images are projected superimposed onto the same screen through orthogonal polarizing filters (Usually at 45 and 135 degrees). [1] The viewer wears linearly polarized eyeglasses which also contain a pair of orthogonal polarizing filters oriented the same as the projector. As each filter only passes light which is similarly polarised and blocks the orthogonally polarized light, each eye only sees one of the projected images, and the 3D effect is achieved. Linearly polarised glasses require the viewer to keep his or her head level, as tilting of the viewing filters will cause the images of the left and right channels to bleed over to the opposite channel. This can make prolonged viewing uncomfortable as head movement is limited to maintain the 3D effect.

A linear polariser converts an unpolarised beam into one with a single linear polarisation. The vertical components of all waves are transmitted, while the horizontal components are absorbed and reflected. Wire-grid-polarizer.svg
A linear polariser converts an unpolarised beam into one with a single linear polarisation. The vertical components of all waves are transmitted, while the horizontal components are absorbed and reflected.

Circularly polarized glasses

To present a stereoscopic motion picture, two images are projected superimposed onto the same screen through circular polarizing filters of opposite handedness. The viewer wears eyeglasses which contain a pair of analyzing filters (circular polarizers mounted in reverse) of opposite handedness. Light that is left-circularly polarized is blocked by the right-handed analyzer, while right-circularly polarized light is blocked by the left-handed analyzer. The result is similar to that of stereoscopic viewing using linearly polarized glasses, except the viewer can tilt his or her head and still maintain left/right separation (although stereoscopic image fusion will be lost due to the mismatch between the eye plane and the original camera plane).

Circular polarizer passing left-handed, counter-clockwise circularly polarized light Circular.Polarization.Circularly.Polarized.Light Circular.Polarizer Passing.Left.Handed.Helix.View.svg
Circular polarizer passing left-handed, counter-clockwise circularly polarized light

As shown in the figure, the analyzing filters are constructed of a quarter-wave plate (QWP) and a linearly polarized filter (LPF). The QWP always transforms circularly polarized light into linearly polarized light. However, the angle of polarization of the linearly polarized light produced by a QWP depends on the handedness of the circularly polarized light entering the QWP. In the illustration, the left-handed circularly polarized light entering the analyzing filter is transformed by the QWP into linearly polarized light which has its direction of polarization along the transmission axis of the LPF. Therefore, in this case the light passes through the LPF. In contrast, right-handed circularly polarized light would have been transformed into linearly polarized light that had its direction of polarization along the absorbing axis of the LPF, which is at right angles to the transmission axis, and it would have therefore been blocked.

By rotating either the QWP or the LPF by 90 degrees about an axis perpendicular to its surface (i.e. parallel to the direction of propagation of the light wave), one may build an analyzing filter which blocks left-handed, rather than right-handed circularly polarized light. Rotating both the QWP and the LPF by the same angle does not change the behaviour of the analyzing filter.

System construction and examples

Functional principle of polarized 3D systems Passive-3d-tv-technology.jpg
Functional principle of polarized 3D systems

Polarized light reflected from an ordinary motion picture screen typically loses most of its polarization, but the loss is negligible if a silver screen or aluminized screen is used. This means that a pair of aligned DLP projectors, some polarizing filters, a silver screen, and a computer with a dual-head graphics card can be used to form a relatively high-cost (over US$10,000 in 2010) system for displaying stereoscopic 3D data simultaneously to a group of people wearing polarized glasses.[ citation needed ]

In the case of RealD a circularly polarizing liquid crystal filter which can switch polarity 144 times per second [2] is placed in front of the projector lens. Only one projector is needed, as the left and right eye images are displayed alternately. Sony features a new system called RealD XLS, which shows both circularly polarized images simultaneously: A single 4K projector displays two 2K images one above the other, a special lens attachment polarizes and projects the images on top of each other. [3]

Optical attachments can be added to traditional 35 mm projectors to adapt them for projecting film in the "over-and-under" format, in which each pair of images is stacked within one frame of film. The two images are projected through different polarizers and superimposed on the screen. This is a very cost-effective way to convert a theater for 3-D as all that is needed are the attachments and a non-depolarizing screen surface, rather than a conversion to digital 3-D projection. Thomson Technicolor currently produces an adapter of this type. [4]

When stereo images are to be presented to a single user, it is practical to construct an image combiner, using partially silvered mirrors and two image screens at right angles to one another. One image is seen directly through the angled mirror whilst the other is seen as a reflection. Polarized filters are attached to the image screens and appropriately angled filters are worn as glasses. A similar technique uses a single screen with an inverted upper image, viewed in a horizontal partial reflector, with an upright image presented below the reflector, again with appropriate polarizers.[ original research? ]

On TV and computer screens

Polarizing techniques are easier to apply with cathode ray tube (CRT) technology than with Liquid crystal display (LCD). Ordinary LCD screens already contain polarizers for control of pixel presentation — this can interfere with these techniques.

In 2003 Keigo Iizuka discovered an inexpensive implementation of this principle on laptop computer displays using cellophane sheets. [5]

One can construct a low cost polarized projection system by using a computer with two projectors and an aluminium foil screen. The dull side of aluminium foil is brighter than most silver screens.[ citation needed ] This was demonstrated at PhraJomGlao University, Nônthaburi, Thailand, September 2009.

Health care

In optometry and ophthalmology, polarized glasses are used for various tests of binocular depth perception (i.e. stereopsis).

History

Polarized 3-D projection was demonstrated experimentally in the 1890s. The projectors used Nicol Prisms for polarization. Packs of thin glass sheets, angled so as to reflect away light of the unwanted polarity, served as the viewing filters. [6] Polarized 3-D glasses only became practical after the invention of Polaroid plastic sheet polarizers by Edwin Land, who was privately demonstrating their use for projecting and viewing 3-D images in 1934. [7] They were first used to show a 3-D movie to the general public at "Polaroid on Parade", a New York Museum of Science and Industry exhibit that opened in December 1936. 16 mm Kodachrome color film was used. [8] [9] [10] Details about the glasses are not available. At the 1939 New York World's Fair, a short polarized 3-D film was shown at the Chrysler Motors pavilion and seen by thousands of visitors daily. The hand-held cardboard viewers, a free souvenir, were die-cut in the shape of a 1939 Plymouth seen head-on. Their Polaroid filters, stapled over rectangular openings where the headlights ought to be, were very small. [11]

Cardboard glasses with earpieces and larger filters were used to watch Bwana Devil , the feature-length color 3-D film that premiered on 26 November 1952 and ignited the brief but intense 3-D fad of the 1950s. The well-known Life magazine photo of an audience wearing 3-D glasses was one of a series taken at the premiere. [12] [13] The film's title, imprinted on the earpieces, is plainly visible in high-resolution copies of those images. Imaginatively colorized versions have helped to spread the myth that the 3-D movies of the 1950s were projected by the anaglyph color filter method. In fact, during the 1950s anaglyph projection was used only for a few short films. Beginning in the 1970s, some 1950s 3-D feature films were re-released in anaglyph form so that they could be shown without special projection equipment. There was no commercial advantage in advertising the fact that it was not the original release format.

Polaroid filters in disposable cardboard frames were typical during the 1950s, but more comfortable plastic frames with somewhat larger filters, considerably more expensive for the theater owner, were also in use. Patrons were normally instructed to turn them in when leaving so that they could be sanitized and reissued, and it was not uncommon for ushers to be stationed at the exits to attempt to collect them from forgetful or souvenir-loving patrons.

Cardboard and plastic frames continued to co-exist during the following decades, with one or the other favored by a particular film distributor or theater or for a particular release. Specially imprinted or otherwise custom-made glasses were sometimes used. Some showings of Andy Warhol's Frankenstein during its 1974 U.S. first run featured unusual glasses consisting of two stiff plastic polarizers held together by two thin silver plastic tubes slit lengthwise, one attached across the tops and bent at the temples to form earpieces, the other a short length bent in the middle and serving as the bridge piece. The design managed to be both stylish in an appropriately Warholesque way and self-evidently simple to manufacture from the raw sheet and tube stock.

Linear polarization was standard into the 1980s and beyond.

In the 2000s, computer animation, digital projection, and the use of sophisticated IMAX 70 mm film projectors, have created an opportunity for a new wave of polarized 3D films. [14]

In the 2000s, RealD Cinema and MasterImage 3D were introduced, both using circular polarization.

At IBC 2011 in Amsterdam RAI several companies, including Sony, Panasonic, JVC & others highlighted their upcoming 3D stereoscopic product portfolios for both the professional and consumer markets to use the same polarization technique as RealD 3D Cinema uses for stereoscopy. These highlighted products cover everything from recording, projecting, viewing and digital display technologies to live, recorded and pre- and post production facilities and soft- and hardware based product to facilitate 3D content creation. Their systems are interoperable and compatible with existing, passive RealD 3D glasses.[ citation needed ]

Advantages and disadvantages

Compared to anaglyph images, the use of polarized 3D glasses produces a full-color image that is considerably more comfortable to watch and is not subject to binocular rivalry. However, it requires a significant increase in expense: even the low cost polarized glasses typically cost 50% more than comparable red-cyan filters, [15] and while anaglyph 3-D films can be printed on one line of film, a polarized film was often done with a special set up that uses two projectors. The use of multiple projectors also raises issues with synchronization, and a poorly synchronized film would negate any increased comfort from the use of polarization. This problem was solved by a number of single strip polarized systems which were standard in the 1980s.

Particularly with the linear polarization schemes popular since the 1950s, the use of linear polarization meant that a level head was required for any sort of comfortable viewing; any effort to tilt the head sideways would result in the polarization failing, ghosting, and both eyes seeing both images. Circular polarization has alleviated this problem, allowing viewers to tilt their heads slightly (although any offset between the eye plane and the original camera plane will still interfere with the perception of depth).

Because neutral-gray linear-polarizing filters are easily manufactured, correct color rendition is possible. Circular-polarizing filters often have a slight brownish tint, which may be compensated for during projection.

Until 2011, home 3D television and home 3D computer primarily used active shutter glasses with LCD or plasma displays. TV manufacturers (LG, Vizio) have introduced displays with horizontal polarizing stripes overlaying the screen. The stripes alternate polarization with each line. This permits using relatively inexpensive passive viewing glasses, similar to those for movies. The principal disadvantage is that each polarization can display only half as many scanning lines.

Advantages

Disadvantages

See also

Related Research Articles

Polarization (waves) property of waves that can oscillate with more than one orientation

Polarization is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. A simple example of a polarized transverse wave is vibrations traveling along a taut string (see image); for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string. In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves in solids.

Stereoscopy Technique for creating or enhancing the illusion of depth in an image

Stereoscopy is a film (non-digital) technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision. The word stereoscopy derives from Greek στερεός (stereos), meaning 'firm, solid', and σκοπέω (skopeō), meaning 'to look, to see'. Any stereoscopic image is called a stereogram. Originally, stereogram referred to a pair of stereo images which could be viewed using a stereoscope.

Slide projector opto-mechanical device for showing photographic slides

A slide projector is an opto-mechanical device for showing photographic slides.

3D films have existed in some form since 1915, but had been largely relegated to a niche in the motion picture industry because of the costly hardware and processes required to produce and display a 3D film, and the lack of a standardized format for all segments of the entertainment business. Nonetheless, 3D films were prominently featured in the 1950s in American cinema, and later experienced a worldwide resurgence in the 1980s and 1990s driven by IMAX high-end theaters and Disney-themed venues. 3D films became increasingly successful throughout the 2000s, peaking with the success of 3D presentations of Avatar in December 2009, after which 3D films again decreased in popularity. Certain directors have also taken more experimental approaches to 3D filmmaking, most notably celebrated auteur Jean-Luc Godard in his films 3X3D

A stereo display is a display device capable of conveying depth perception to the viewer by means of stereopsis for binocular vision.

A silver screen, also known as a silver lenticular screen, is a type of projection screen that was popular in the early years of the motion picture industry and passed into popular usage as a metonym for the cinema industry. The term silver screen comes from the actual silver content embedded in the material that made up the screen's highly reflective surface.

Active shutter 3D system technique of displaying stereoscopic 3D images

An active shutter 3D system is a technique of displaying stereoscopic 3D images. It works by only presenting the image intended for the left eye while blocking the right eye's view, then presenting the right-eye image while blocking the left eye, and repeating this so rapidly that the interruptions do not interfere with the perceived fusion of the two images into a single 3D image.

Anaglyph 3D stereoscopic 3D effect

Anaglyph 3D is the stereoscopic 3D effect achieved by means of encoding each eye's image using filters of different colors, typically red and cyan. Anaglyph 3D images contain two differently filtered colored images, one for each eye. When viewed through the "color-coded" "anaglyph glasses", each of the two images reaches the eye it's intended for, revealing an integrated stereoscopic image. The visual cortex of the brain fuses this into the perception of a three-dimensional scene or composition.

A vectograph is a type of stereoscopic print or transparency viewed by using the polarized 3D glasses most commonly associated with projected 3D motion pictures.

Polarizer Optical filter device

A polarizer or polariser is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. It can filter a beam of light of undefined or mixed polarization into a beam of well-defined polarization, that is polarized light. The common types of polarizers are linear polarizers and circular polarizers. Polarizers are used in many optical techniques and instruments, and polarizing filters find applications in photography and LCD technology. Polarizers can also be made for other types of electromagnetic waves besides light, such as radio waves, microwaves, and X-rays.

Polarizing filter (photography)

A polarizing filter or polarising filter is often placed in front of the camera lens in photography in order to darken skies, manage reflections, or suppress glare from the surface of lakes or the sea. Since reflections tend to be at least partially linearly-polarized, a linear polarizer can be used to change the balance of the light in the photograph. The rotational orientation of the filter is adjusted for the preferred artistic effect. For modern cameras, a circular polarizer (CPL) is typically used; this comprises firstly a linear polarizer which performs the artistic function just described, followed by a quarter-wave plate which further transforms the now-linearly polarized light into circularly-polarised light before entering the camera. This additional step avoids problems with autofocus and light-metering sensors within some cameras, which otherwise may not function reliably with a simple linear polariser.

Aluminized screen may refer to a type of cathode ray tube (CRT) for video display, or to a type of projection screen for showing motion pictures or slides, especially in polarized 3D.

RealD 3D is a digital stereoscopic projection technology made and sold by RealD. It is currently the most widely used technology for watching 3D films in theaters (cinemas). Worldwide, RealD 3D is installed in more than 26,500 auditoriums by approximately 1,200 exhibitors in 72 countries as of June 2015.

Phantograms, also known as Phantaglyphs, Op-Ups, free-standing anaglyphs, levitated images, and book anaglyphs, are a form of optical illusion. Phantograms use perspectival anamorphosis to produce a 2D image that is distorted in a particular way so as to appear, to a viewer at a particular vantage point, three-dimensional, standing above or recessed into a flat surface. The illusion of depth and perspective is heightened by stereoscopy techniques; a combination of two images, most typically but not necessarily an anaglyph. With common (red–cyan) 3D glasses, the viewer's vision is segregated so that each eye sees a different image.

Leonard "Lenny" Lipton is an American author, filmmaker, lyricist and inventor. At age 19, Lipton wrote the poem that became the basis for the lyrics to the song "Puff the Magic Dragon". He went on to write books on independent filmmaking and become a pioneer in the field of projected three-dimensional imagery. His technology is used to show 3D films on more than 25,000 theater screens worldwide.

3D television Television that conveys depth perception to the viewer

3D television (3DTV) is television that conveys depth perception to the viewer by employing techniques such as stereoscopic display, multi-view display, 2D-plus-depth, or any other form of 3D display. Most modern 3D television sets use an active shutter 3D system or a polarized 3D system, and some are autostereoscopic without the need of glasses. As of 2019, most 3D TV sets and services are no longer available.

Dolby 3D marketing name

Dolby 3D is a marketing name for a system from Dolby Laboratories, Inc. to show three-dimensional motion pictures in a digital cinema.

ColorCode 3-D is an anaglyph 3D stereoscopic viewing system deployed in the 2000s that uses amber and blue filters. It is intended to provide the perception of nearly full colour viewing with existing television, digital and print mediums. Danish company ColorCode 3-D ApS distributes the system, and says that it is covered by a number of patents around the world including US patent 6687003.

MasterImage 3D

MasterImage 3D is a company that develops stereoscopic 3D systems for theaters, and auto-stereoscopic 3D displays for mobile devices.

FPR is a technology promoted by LG that is employed in its line of 3D televisions based on circular polarization. It shows left and right images through different patterns in a circular polarizer. Left/right polarized glasses allow the left and right images to then be seen by the left and right eyes separately. Both images are combined in the brain and generate the 3D effect. The FPR technology uses the precise film which polarizes different pixels differently to show a different image for each eye. FPR 3D tech is said to deliver a brighter screen with less cross talk, less ghosting, and no flickering.

References

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  2. Cowan, Matt (5 December 2007). "REAL D 3D Theatrical System" (PDF). European Digital Cinema Forum. Archived from the original (PDF) on 5 April 2017. Retrieved 5 April 2017.
  3. "Sony – Market Professional". sony.com.
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  7. Zone, op. cit., p. 150
  8. McElheny, Victor K (1998). Insisting On the Impossible, The Life of Edwin Land, Inventor of Instant Photography, Perseus Books, p. 114
  9. Zone, op. cit., pp. 152-153
  10. Note: some sources state that the Italian feature film Nozze Vagabonde, filmed in 3-D in 1936, was shown by polarized projection in that year, but no contemporary evidence of any kind has yet been presented to support the claim; other sources state that anaglyph projection was used, or that the 3-D version was never shown to the public at all. Sources agree that polarized projection was used for the German short Zum Greifen nah, filmed in 1936 with a single-strip 3-D system, but it was not shown to the public until 1937.
  11. Zone, op. cit., p. 158 illustrates the viewers given out during the 1940 season of the Fair. The 1939 variety depicted the earlier model car head-on but the filters were identical.
  12. Getty Images #2905087 One of several photographs taken by J. R. Eyerman at the Bwana Devil premiere.
  13. Getty Images #50611221 One of several photographs taken by J. R. Eyerman at the Bwana Devil premiere.
  14. Manjoo, Farhad. A look at Disney and Pixar's 3-D movie technology. 2008.04.09. Downloaded 2009.06.07
  15. Price list showing paper linear polarized glasses at 3 for $2, anaglyph 2 for $1 http://www.berezin.com/3d/3dglasses.htm
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